1 files changed, 81 insertions, 0 deletions
diff --git a/ext/mixed/js/task-accumulator.js b/ext/mixed/js/task-accumulator.js
new file mode 100644
index 00000000..5c6fe312
--- /dev/null
+++ b/ext/mixed/js/task-accumulator.js
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2020  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+class TaskAccumulator {
+    constructor(runTasks) {
+        this._deferPromise = null;
+        this._activePromise = null;
+        this._tasks = [];
+        this._tasksActive = [];
+        this._uniqueTasks = new Map();
+        this._uniqueTasksActive = new Map();
+        this._runTasksBind = this._runTasks.bind(this);
+        this._tasksCompleteBind = this._tasksComplete.bind(this);
+        this._runTasks = runTasks;
+    }
+
+    enqueue(key, data) {
+        if (this._deferPromise === null) {
+            const promise = this._activePromise !== null ? this._activePromise : Promise.resolve();
+            this._deferPromise = promise.then(this._runTasksBind);
+        }
+
+        const task = {data, stale: false};
+        if (key !== null) {
+            const activeTaskInfo = this._uniqueTasksActive.get(key);
+            if (typeof activeTaskInfo !== 'undefined') {
+                activeTaskInfo.stale = true;
+            }
+
+            this._uniqueTasks.set(key, task);
+        } else {
+            this._tasks.push(task);
+        }
+
+        return this._deferPromise;
+    }
+
+    _runTasks() {
+        this._deferPromise = null;
+
+        // Swap
+        [this._tasks, this._tasksActive] = [this._tasksActive, this._tasks];
+        [this._uniqueTasks, this._uniqueTasksActive] = [this._uniqueTasksActive, this._uniqueTasks];
+
+        const promise = this._runTasksAsync();
+        this._activePromise = promise.then(this._tasksCompleteBind);
+        return this._activePromise;
+    }
+
+    async _runTasksAsync() {
+        try {
+            const allTasks = [
+                ...this._tasksActive.map((taskInfo) => [null, taskInfo]),
+                ...this._uniqueTasksActive.entries()
+            ];
+            await this._runTasks(allTasks);
+        } catch (e) {
+            yomichan.logError(e);
+        }
+    }
+
+    _tasksComplete() {
+        this._tasksActive.length = 0;
+        this._uniqueTasksActive.clear();
+        this._activePromise = null;
+    }
+}